You can refresh a tired looking kitchen in a number of ways, one of them is by fitting new worktops but at an average of £80 a length fooking the cuts can get expensive. Here's a few tips...
Getting a good finish means using 'routed joints' - that is, you use a router to create the joints and use clamps underneath to pull them together. Then apply colour sealant to the joins. To do this you'll need a router jig and a new bit (and a router, obs).
Cut the lengths first i.e. you have a U-shape, cut the sides of the U first. Tip: buy a square for a couple of quid
Your kitchen will not be plumb nor will it be square - get over it!
Measure the back length for the worktop then the front length. Use the square to determine how much adrift they are - use the edge of a level to measure how far away from square the walls are i.e. 2mm on the left, 5mm on the right. Now, turn the work top upside down and mark it up - it's easier to see the mark on the light colour of the underside. Throw the jigsaw back in the garage Use a circular saw and cut with the worktop UPSIDE-DOWN! The saw cuts up, that smashes the top but the top will be DOWN 'cos it's the underneath
Once you have the two sides of the U, set up the jig ready for the routed joins. The jig costs £80-100 but OMG does it save some grief. You need two clamps, the jig comes with dowels, line up the dowels with the worktop and clamp in place. Read the instructions that came with the jig No comprendo - post here and I'll explain more!
Then you can measure up the bottom of the U - same principles apply.
Drop the worktops in place and clamp using the u-bolts provided.
Now it's time to cut out for sink/hob etc. Do NOT take the worktops out! Cut them in place - a big hole = a weak worktop, you'll break it!. Lock the jigsaw in the garage and give the missus the key
Measure twice, three times, be absolutely convinced. Not sure? Measure again! Oh, it's a dark worktop? Use masking tape applied in approximately the correct position and mark the tape - you MUST be able to see the cut line.
Use a 25mm flat bit to cut out the corners, keep checking underneath for the point. If at all possible, when you see the point, drill from underneath about 2mm into the underside of the worktop. Back to the top. Drill the rest of the way through easing off as you approach the end - avoids big lumps being smashed out
Using a circular saw cut the main runs - angle the saw on the bed (the flat bit that the blade sticks out of), manually withdraw the guard, angle the saw blade so it is just short of the previously cut 25mm holes, if you can't get clearance for the saw use supporting timbers to rest the worktop on so you can move it around - these should be long lengths to avoid any 'sag' in the worktop. Don't push too hard, fine cuts need gentle fingers.
With the worktop in its final position the missus can release the jigsaw - do the final cuts into the corners and remove the waste.
Clamp worktops back up, screw back to units and apply jointing colour.
Perfect cut, unbroken worktop, job done